1. Field of the Invention
The present invention relates to a liquid crystal display panel, and more specifically, to a liquid crystal on silicon display panel capable of preventing sealant from contaminating liquid crystal molecules.
2. Description of the Prior Art
A liquid crystal on silicon (LCOS) display panel is a liquid crystal display panel comprising a pixel cell matrix, driving ICs, and other electric elements on a silicon substrate and fabricated by semiconductor processes. It has the advantages of having small pixel sizes, high brightness, high resolution, simple fabricating processes, low cost, and a small volume. Therefore the LCOS display panels have been applied to video and media equipments, such as handy cameras, web mobile phones, projection TVs, and multi-media overhead projectors.
Please refer to FIG. 1 and FIG. 2. FIG. 1 is a top view of an LCOS display panel according to the prior art. FIG. 2 is a sectional view along line 2-2 of the LCOS display panel shown in FIG. 1. As shown in FIG. 1 and FIG. 2, an LCOS display panel 10 includes a glass substrate 12, which is not shown in FIG. 1 but in FIG. 2 for avoiding confusion, a silicon substrate 14 in parallel with and opposite to the glass substrate 12, and a liquid crystal layer 18 formed between the glass substrate 12 and the silicon substrate 14. Additionally, the LCOS display panel 10 further includes an alignment layer 16a located between the glass substrate 12 and the liquid crystal layer 18, and an alignment layer 16b positioned between the silicon substrate 14 and the liquid crystal layer 18. The alignment layers 16a and 16b function to adjust orientations of liquid crystal molecules. The LCOS display panel 10 further includes a sealant 20 surrounding the liquid crystal layer 18 for adhering the silicon substrate 14 to the glass substrate 12. The sealant 20 is usually mixed with silica balls for providing a constant distance between the glass substrate 12 and the silicon substrate 14.
However, the traditional sealant material used in industries may react with the liquid crystal molecules as influencing by the factors of temperature and time or other process factors. It seriously affects the orientations and twists of the liquid crystal molecules in defects and causes contaminations. In this situation, when a common voltage is applied to the liquid crystal layer 18, the liquid crystal molecules near the sealant 20 twist in a different direction from other liquid crystal molecules, and it results in that the display image near the sealant 20 differs from the other positions of the LCOS display panel 10, causing the mura problem, and in decreasing the display performance of the LCOS display panel 10. Furthermore, when the alignment layers 16a, 16b are formed of inorganic materials, such as silicon dioxide (SiO2) or silicon nitride (SiNx), the twist direction of the liquid crystal molecules is even more easily affected by the sealant 20 because of the low anchoring energy between the liquid crystal molecules and the silicon dioxide or the silicon nitride materials.
For solving the mura problem resulting from the sealant 20, the prior art used to increase the distance between the sealant 20 and the active region 14a. However, this reduces the display area of the LCOS display panel 10 or increases the die size of the LCOS display panel 10. Therefore, it is still an important issue to prevent the sealant 20 from contaminating the liquid crystal molecules of the liquid crystal layer 18 so that the display performance of the LCOS display panel 10 can be improved.